This invention generally relates to vascular catheters and, most particularly, to catheters that can be remotely guided or steered by selective deflection of the catheter distal end or tip.
Catheters have been in common use in medical practice for many years. They are often used, for example, to probe locations inside a body lumen which are otherwise unreachable without surgery. A catheter is first inserted into a major vein or artery, or other body lumen, which is near the surface of the patient's body. The catheter is then guided to the area of concern by further inserting it into the body lumen. As medical knowledge increases, more uses of catheters have been developed and these uses have become more complex so that the ability to accurately and selectively steer the distally-located tip of the catheter has become of extreme importance. For example, there is a need to use steerable catheters to apply electrical pulses and the like to various internal, electrically excitable body tissues, such as the heart. Similarly, there is also a need to measure electrical currents existing in various body tissues and organs, such as the heart.
In order to place the tip of the catheter in the correct location and position, it is necessary to curve the tip of the catheter so that the catheter's distal end or tip will travel into the proper branch of a vascular lumen as the catheter is inserted. After the tip has been so curved, it is also often desirable to rotate the catheter's tip while maintaining the catheter tip's curvature so that the tip can then approach and contact the tissue of interest. In addition, once the catheter's tip has contacted the tissue of interest, it is also important that the tip make firm contact with the tissue so that an electrical current can be reliably applied by the catheter's tip to the tissue. Finally, it is desirable to be able to maintain the curvature of the exact catheter's tip during the procedure with a locking mechanism yet still permit ready, reliable and complete straightening of the catheter's tip upon command. It is also important to enable the user to selectively attain smooth, steady and predictable angular rotation of the tip as the handle or proximal end of the catheter is correspondingly rotated.
In known catheters, when the distal, curved tip must be rotated after encountering an obstruction, rotation of the proximally-located handle does not result in an equal, corresponding rotation of the catheter's distal tip until some threshold angular force or torque has thus been applied to the catheter base. At this point, the catheter tip can suddenly and uncontrollably spin in a jolt of rotation which, at the very least, reduces the angular resolution that is required by studies of the type normally undertaken with these devices.